Battery-powered vehicles, such as electric vehicles or hybrid electric vehicles, may contain one or more high-voltage battery packs connected to a DC bus. The high-voltage battery pack may be used as the primary power source of a vehicle to drive various primary loads (e.g., traction motors) and various auxiliary loads (e.g., HVAC, lighting, pumps, etc.). To ensure high-voltage safety, the high-voltage battery pack must be isolated from the vehicle electrical system when the vehicle is turned off. Consequently, each time when the vehicle is turned on, the high-voltage battery pack needs to be connected to the DC bus. However, because the loads may have a large capacitance and the high-voltage battery pack may only have a small source resistance, initial connection of the high-voltage battery pack may generate a severe inrush current. Such inrush current may easily peak up to, for example, 10,000 A in typical vehicle settings, and may damage electrical components of the vehicle.
To limit the inrush current, a pre-charge circuit may be coupled between the high-voltage battery pack and the DC bus to pre-charge the bus capacitance before the high-voltage battery pack is fully connected to the DC bus. Conventionally, the pre-charge circuit may include a pre-charge resistor and a pre-charge contactor (or relay) connected in series. During operation, the pre-charge contactor may be closed to connect the pre-charge resistor to the high-voltage battery pack, so as to limit the inrush current. However, the high power pre-charge contactor is an expensive and bulky component. It not only increases the cost of the vehicle, but also is difficult to package in the limited space of the vehicle.
The disclosed system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.